The Alkaline Diet Myth

Updated 1/1/2019

There are more diet plans out there than anyone could possibly count. One diet plan that’s based completely on an incorrect understanding biology is the alkaline diet. The idea behind this diet is that certain foods help to maintain your body in a non-acid state. Somehow this promotes weight loss and general well-being. If you’ve taken a chemistry class, you probably are scratching your head right now. The human body is actually maintained in a very slightly alkaline state. Let’s look at what that means so that we can figure out why this diet makes no sense.

pH is typically defined as the negative log of the hydronium ion concentration in a solution. Hydronium is produced whenever an Arrhenius acid is dissolved in water. “Arrhenius acid” is just the term for hydrogen producing acids. Don’t worry about that. It might be easier to imagine from a reaction standpoint. Take this for example: sulfuric acid (H2SO4) dissolved in pure water (pH 7.00) will produce positively charged hydronium (H30) and negatively charged sulfate ions (SO4). It may be easier to imagine the H2SO4 just breaking apart into H2 and SO4. Free protons don’t like to exist in water so the hydrogen atoms react with the water to create hydronium. The hydronium concentration goes up which, when you take the negative base10 logarithm of it, will give you a number lower than 7.00.

The pH scale goes from 0 to 14 with the low end indicating an acid and the high end indicating a base (alkaline). In a system where the pH is 7, that means there is an equal concentration of hydronium and hydroxyl. Hydroxyl (OH) is just the opposite of hydronium. When you dissolve an Arrhenius base in water, it produces hydroxyl. Whenever hydroxyl and hydronium are combined, they form water through a process called auto-ionization.

Neat, huh?

The Alkaline Diet conveniently ignores the actual pH of the items in this picture.
The Alkaline Diet conveniently ignores the actual pH of the items in this picture.

Ok, let’s talk diet. These diets are based on the idea that they somehow alter your body chemistry to promote weight loss. There’s only two ways that your blood pH can change. These methods of pH control are the respiratory and renal systems.

Your respiratory system modifies bicarbonate levels (which is a reactant in the chemical equation that produces carbonic acid) by increasing or decreasing CO2 uptake from the lungs. This is a quick process which is the primary moderator of blood pH.

Your renal system increases or decreases the uptake of hydrogen and bicarbonate levels by your kidneys. This is a much more gradual process.

Guess what?  These two systems completely nullify any type of impact that your diet has on your blood pH.

How important is blood pH? As it turns out, pretty important. Enzymatic reactions in your body require an extremely tight control band for your blood pH (7.35-7.45). If you wander outside of this band, denaturing of enzymes and protein may occur resulting in metabolic processes no longer working correctly. This is about as severe as suffering from hypothermia in terms of chance of death. The homeostatic processes in your body aren’t quite working anymore which is a very bad thing. The medical term for suffering from an incorrect blood pH is either acidosis/acidemia or alkalosis.

This next bit is from a reader, David Jack, MLT(ASCP).

Blood pH can not only be set out of whack due to respiratory or renal reasons. There are a few more reasons as well. Ketoacidosis manifests fairly often (especially diabetic ketoacidosis). Ketone bodies pumped out by the liver when the body is not utilizing glucose for energy pushes pH down. The body WILL begin to compensate either through the lung or kidneys (usually both in these cases), but neither is involved in the initial state response. Some drugs given through IV can also impact pH. Usually something like sodium bicarbonate will also be administered along with it as a buffer.

So no, most people’s bodies are not out of pH balance and those who are are experiencing acidosis or alkalosis and are probably in the hospital suffering from acidemia (low blood pH). At low levels, you may find yourself feeling nausea, numbness, muscle spasms, and hand tremors. At more severe levels you will feel increasing dizziness, difficulty breathing, confusion, stupor, and eventually going into a coma.

How do you prevent this? Stay hydrated! Otherwise you should never be concerned about this unless you’re suffering from particular respiratory or kidney diseases.